Topic 2 population genetics

Question 1

Phenotypes are determined by a combination of:

Answer 1

Genetics (heritable)

Environment

Question 2

Alleles defined

Answer 2

• Individuals have 2 sets of chromosomes
• Each chromosome has a sequence of genes along its length.
• Alleles -

Question 3

Define Homozygous

Answer 3

the same allele on both chromosomes.

Question 4

Define heterozygous:

Answer 4

: different alleles on both chromosomes.

Question 5

What is gene pool

Answer 5

It all the alleles present in the population

Question 6

What aspects of heterozygosity

Depend

Answer 6

• number of alleles available
• size of the population
• mating practices (clonal or sexual)
• migration patterns

Question 7

What is Hardy-Weinberg equilibrium consist of

Answer 7

• Random mating
• No mutations
• No natural selection
• No gene flow
• A large breeding population

Question 8

Genetic drift

Answer 8

• The fluctuation of allele frequencies due to chance alone
• Occurs in all populations, but has a stronger effect in small populations
• Extreme form - Can lead to the loss of
alleles, or fixation

Question 9

What causes genetic drift

Answer 9

• Small populations
• Random disturbances - big storm, volcano
• Founder effects
• Bottlenecks

Question 10

Founder effect

Answer 10

Individuals that disperse to a new area to found a new population have a subset of the alleles from the entire population, leading to a large change in allele frequencies. (i.e insects on branch)

Question 11

Bottleneck effect

Answer 11

A rapid decrease in population size due to a disturbance or natural disaster removes some genotypes from the population, altering allele frequencies.

Question 12

What are outcomes of non

Random mating

Answer 12

Positive assortative mating – Mate choice is based on similarity of phenotype

2. Negative assortative mating – Mate choice is based on dissimilarity of phenotype
3. Inbreeding – Mating with relatives at a rate greater than expected by chance

Question 13

Negative assertive mating

Answer 13

• Avoid mating with individuals that are like yourself, either phenotypically or genetically.
• Common in Plants (Self-incompatibility)
– Stop pollen germination, or pollen tube growth
• Animals (i.e. Drosophila -fruit flies)
– Rare male advantage - females prefer males with the rarest phenotype.
– Pheromonally test each other

Question 14

what is a disease caused due to interbreeding

Answer 14

• hemophilia
  Managing endangered species –low
  heterozygosity = low population
  robustness

Question 15

what organisms mate via selfing

Answer 15

Plants - selfing can occur in
plants that self-pollinate
(Gregor Mendel’s peas)
Animals - in snails and
other animals that can selffertilise

Question 16

what is gene flow

Answer 16

The transmission of traits or

genes between populations

Question 17

what is the impact of geneflow

Answer 17

Gene flow tends to reduce
differences between populations
• Rates of gene flow vary widely:
compare birds to ants, sharks to
moss
• Good- increases genetic variability
• Bad -Can swamp local selection
pressure, making populations less
adapted
(i.e. mountain and valley eucalypts)

Question 18

difference between genetic drift and gene flow

Answer 18

Genetic Drift and Gene
flow are opposing forces:
drift creates differences
between populations and
gene flow reduces
differences between
populations

Question 19

what is the advantage of genetic drift

Answer 19

Genetic drift can by
chance increase the
frequency of an
advantageous allele to the
point where natural
selection can be more
effective

Question 20

define Clade

Answer 20

A group of organisms
that have a common
ancestor i.e all mammals
have hair

Question 21

what is Monophyletic clade

Answer 21

a
clade that includes a
common ancestor and all its
descendants.